Magnetically controlled firing mechanism for marine mines



March .1, 1955 J. B. GLENNON ETAL MAGNETICALLY CONTROLLED FIRINGMECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet 1 i. 1MB

ZIWuQ/W'IMS J. B- GLENNON C. M. VAN ATTA F. W. BROWN Ill March 1, 1955.1. B. GLENNON ET AL MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINEMINES 8 Sheets-Sheet 2 Filed July 1, 1942 ll/llilll! r114! glwuonfoz J.'B. GLENNON c. M. VAN ATTA F. w. BROWN m March 1, 1955 J. B. GLENNON ETAL 2,703,052

MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES 8 Sheets-Sheet(5 Filed July 1, 1942 GLENNON VA N ATTA BROWN m March 1, 1955 J. B.GLENNON ET AL MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES8 Sheets-Sheet 4 Filed July 1, 1942 mmm QrWQ/WY/MS J B. GLENNON C. M,VAN ATTA F. W. BROWN Ill //////vv//// Q issan-=5 March 1, 1955 J. B.GLENNON ET AL 2,703,052 MAGNETICALLY CONTROLLED FIRING MECHANISM FORMARINE MINES Filed July 1, 1942 8 Sheets-Sheet 5 m m N awn M3041 J. B,GLENNON G. M. VAN ATTA F. W. BROWN lll March 1 @555 a. a GLENNON ETAL2,703,052

MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July 1,1942 8 Sheets-Sheet 6 F. w. BROWN m March 1, 1955 .1. B. GLENNON ETAL 93 MAGNETICALLY CONTROLLED FIRING MECHANISM FOR MARINE MINES Filed July1, 1942 8 Sheets-Sheet '7 J. B. GLENNQN C. M. VAN ATTA F. W. BROWN HIMarch 1, 1955 J. B. GLENNON ET AL 2,73@52 MAGNETICALLY CONTROLLED FIRINGMECHANISM FOR MARINE MINES Filed July 1, 1942 8 Sheets-Sheet 8 arm 0W5J. B. GLENNQN C. M. VAN ATTA W. BROWN Ill yk wi MAGNETICALLY CONTROLLEDFIRING NECHANISM FOR E MINES James B. Glennon, Washington, D. C.,Chester M. Van Atta, Bethesda, Md., and Frank W. Brown III, Rome, N. Y.

Application July 1, 1942, Serial No. 449,310

21 (Ilaims. (Cl. 102-18) (Granted under Title 35, U. S. Code (1952),see. 266) This invention relates to magnetically controlled firing ttesatent mechanisms for marine mines in which a pivoted magnetic needle orbar is moved from a predetermined setting under or by the magneticattraction or influence of a mass of magnetic material within thevicinity of the mine to a firing position thereby to close a circuitfrom a source of electrical energy to an electro-responsive detonatingdevice and explode the mine. More specifically, the magnetized elementis automatically set to a predetermined sensitivity in accordance withthe latitude at which the mine is planted whereby the magnetized elementis adapted to be moved in either direction in a vertical plane inresponse to the approach or passage of a steel vessel within thevicinity of the mine sufiicient to establish a circuit connection from asource of electrical energy to an electro-responsive detonating devicethereby to operate the device and fire the mine.

It may be stated that the lines of force comprising the earths magneticfield are perpendicular to the surface of the earth at the north andsouth magnetic poles, parallel to the earth at the magnetic equator andatan angle with the earths surface at different locations intermediatethe equator and the magnetic poles depending upon the latitude of thelocation. If a balanced magnetic needle or bar be pivoted for rotationin a vertical plane, the needle will assume a position in accordancewith the direction of the lines of magnetic force adjacent thereto at anangle with the surface of the earth depending upon the latitude in whichthe needle is placed, this angle of deviation from the horizontal planebeing hereinafter referred to as the angle of inclination or dip of theneedle.

It has been well established that within the vicinity of a 2,703,052Patented Mar. 1, 1955 "ice above the mine. Such systems have not beenfound to be entirely satisfactory in cases where the vessel has beendegaussed sufficiently to prevent movement of the magnetized needle intothe firing position or in cases where the vessels have beenoverdegaussed for the reason that the magnetic needle is moved by themagnetic field set up by the overdegaussed vessel in a direction toincrease the degree of separation between the firing contacts thereof.

In the system of the present invention a pivoted magnetic elementcomprising a pair of magnetized bars is yieldably held in a positionpreferably at a small angle with respect to a horizontal plane by anadjustable hair spring connected thereto such that the'firing contactelement thereof is normally at rest intermediate a pair of contactingelements. The adjustable hair spring is connected .at the other endthereof to a clockwork mechanism which regulates the torque applied tothe magnetized element such that a change in either direction in themagnetic field adjacent thereto causes the firing contact associatedwith the magnetized element to be moved selectively in steel vessel thelines of force of the earths magnetic field are distorted such that theintensity of the earths magnetic field within the vicinity of the vesselis altered. When such a vessel passes over a submarine mine having amagnetic dip needle therein, the angle of dip of the needle will vary inaccordance with the degree of distortion of the earths magnetic fieldvariably in accordance with the relative position of the vessel withrespect to the mine.

It has also been found that a steel vessel has a certain 7 amount ofmagnetism imparted thereto during the construction of the vessel andacquires certain additional magnetic properties by reason of themovement of the vessel through the earths magnetic field particularlywhen the vessel is moved generally in an east-west directionor viceversa. This magnetic property which the vessel acquires is usually of apredetermined magnetic polarity and may be compensated for to aconsiderable degree by wrapping an electrical cable about the vessel andpassing an electrical current through the cable thereby to dey,magnetize the vessel, such demagnetizing process being herein referredto as degaussing and the vessel to which this process has been appliedas a degaussed vessel. In magnetically controlled systems of the typeheretofore proposed for firing a marine mine such, for example, as

either direction into engagement with the upper or lower contactelement, as the case may be, this adjustment of the hair spring beingreferred to herein as the sensitivity or sensitivity setting of themagnetic element.

It has been found that a degaussed vessel produces certain variations inthe magnetic field opposite a point of reference as the vessel movespast the reference point by reason of the unequal distribution of themagnetic material comprising the vessel and the various masses ofmagneticmaterial carried thereby or secured thereto and it has been thepractice in certain cases to apply an excess of demagnetizing currentthrough the aforesaid cable thereby to impart apredetermined magneticpolarity to the vessel sufiicient to insure the safe passage of thevessel above mines in which the magnetic changes required to fire themines are of the opposite polarity only. By employing a magneticallycontrolled mechanism in which movement of the magnetized bar in eitherdirection from a predetermined setting thereof is employedto fire themine, the possibility of the safe passage of a degaussed vesselthereover is extremely remote for the' reason that certain variations inthe magnetic field of the vessel are found to be present afterthedegaussing process has been completed.

One of the objects of the present invention is to provide a mine firingcontrol mechanism in which relatively small changes in the verticalcomponent of the earths magnetic field of either polarity are employedto fire the mine.

Another object is the provision of new and improved means for preventingthe premature explosion of the mine by countermining operations.

Another object is the provision of new and improved means forautomatically and yieldably adjusting a pivoted magnetic element to apredetermined setting such that a mine firing circuit is closed by apredetermined change in the vertical component of the earths magneticfield adjacent thereto of increased or diminished strength, as the casemay be, regardless of the latitude at which the mine g is planted. 1

Still another of the objects is the provision of a new and improvedmagnetic influence mine adapted to be fired by predetermined changes ofeither polarity in the earths magnetic field adjacent thereto in whichthe arrangement of parts and instrumentalities therefor comprises astructure of simple and rugged construction which is economical tomanufacture and which possesses the desired qualities of reliability andefficiency in use and operation.

Still other objects, advantages and improvements will be apparent fromthe following detailed description taken in connection with theaccompanying drawings of which:

Fig. 1 is a view in section partly broken away of a mine employing thedevice of the present invention in accordance with a preferredembodiment thereof;

Fig. 2 is a greatly enlarged view in section partly broken away of thefiring control mechanism of Fig. 1; Fig. 3 is a greatly enlarged view inelevation partly broken away of the firing control mechanism showing,

among other elements, the latitude setting device em ployed forcontrolling the sensitivity adjustment of the magnetic element;

Fig, 4 is a sectional view taken substantially on the line 44 of Fig. 3;

5 is a sectional view taken on the line 5'-5 of Fig. 6 is a view insection taken substantially along the line 6-6 of Fig. 4;

Fig. 7 is a view in elevation of the magneticelement and certainsupporting and control elements therefor with the cover removed;

Fig. 8 is a view. of the reverse side of the device shown in Fig. 7;

Fig. 9 is an enlarged view partly broken away and partly 'in section ofthe magnetic element of Fig. 4 and certain supporting and controldevices therefor with the magnetic element in a released position;

Fig. 10 is a view in elevation of hte trip switch mechanism 'of Fig. 3;

Fig. 11 is an end view of the trip switch mechanism of Fig. 10 showingthe control elements and supporting plate therefor in section;

Fig. 12 is a view taken substantially along the line 12-42 of Fig. 11;

Fig. 13 is a view taken substantially along the line 13--13 of Fig. 11;

Fig. 14 is a view taken substantially along hte line 1414 of Fig. 9;and,

Fig. 15 illustrates diagrammatically the electrical circuit arrangementof the entire system.

Referring now to the drawings in which like numerals of reference areemployed to designate like parts throughout the several views and moreparticularly to Fig. 1 thereof on which is shown a submarine mineindicated by the numeral 10 according to a preferred embodiment of theinvention comprising a casing 11 having recessed portions 12 and 13therein within which is arranged an extender hydrostat and clockhydrostat respectively. The extender hydrostat comprises a plunger 14slideably supported within the member 15 and normally urged out-. wardby the spring 16 arranged thereon, the plunger being in engagement withthe flexible diaphragm 17 secured in watertight relation with respect tothe casing of the mine as by the bolts 18 and retaining ring 19'. Theplunger 14 supports at one end thereof a detonating device 21 adapted tobe inserted within a booster charge- 22 arranged within the well 23 asthe hydrostat operates, the well being preferably braced to the casingof the mine as by the support 24.

Arranged within the recessed portion 13 of the mine casing is a member25 adapted to support slideably a plunger 26 yieldably urged outward bya spring 27 into engagement with the flexible diaphragm 28 secured inwatertight relation with respect to the'casing of the mine as by thebolts 29 and retaining ring 31. A starting clock or timing mechanism 32,hereinafter referred to as TM, is secured to the member 25 as by thebolts 33 in operative relation with respect to the plunger 26 wherebythe timing mechanism is adapted to be set in operation by movement ofthe plunger inward in response to the pressure of the water against theflexible diaphragm 28.

There is also provided within the casing of the mine a chamber 34 withinwhich is arranged a timing device 35, hereinafter referred to as TD2.The chamber 34 is in communication with the Well 23 as by the tube orduct 36 extending therebetween. A terminal box 37 is also preferablyarranged within the chamber 34 having a plurality of electrical cablesconnected thereto for establishing circuit connections to the startingclock 32, the detonating device 21 and the timing device 35. There isalso connected to the terminal box 37 a pair of conductors 38 and 39connected at the other end thereof to the battery 41 hereinafterreferred to as BA, suitable apertures being provided within the plate orpartition 42 Within which the conductors 38 and 39 are arranged. Thebattery 41 is arranged within the chamber 43 and preferably insulatedtherefrom as by the cushion or yieldable pad 44 thereby to preventinjury or damage to the battery as the mine is launched. The pad 44 maybe composed of any material suitable for the purpose such, for example,as felt, rubber or any of the synthetic placed by a clamping device toprevent movement of the battery relative to the chamber 43 duringhandling, transportation or planting of the mine. There is also providedwithin the mine case a suitable partition 45 thereby to form a chamber46 within which is arranged the firing control mechanism 47 andyieldably supported with respect thereto as by the yieldable pad orcushion 48 composed preferably of rubber or'auy of the syntheticvarieties thereof, the pad 48 having an aperture 49 within which isarranged the electrical cable 50 connected at one end thereof to thejunction box 37 for establishing an external electrical connection tothe firing control mechanism, the partition 45 having an aperture 51therein within which the cable is arranged.

The casing of the mine is enclosed at one end thereof by a suitable cap52 secured thereto as by the bolts 53, a gasket 54 being preferablyarranged between the cap and the casing of the mine to insure awatertight joint therebetween. The casing of the mine also comprises achamber 55 within which is disposed an explosive charge 56 of materialsuitable for the purpose such, for example, as material known in the artas TNT or the like, the casing also being provided with a scalableaperture through which the explosive charge is introduced, as is wellknown in the art to which the present invention pertains.

The clock or timing mechanism TM is provided with one or more springmembers 57, Fig. 15, preferably of non-magnetic material suitable forthe purpose such, for example, as Phosphor bronze, beryllium copper, orthe like connected to a gear train having an escapement wheel 58 and anescapement member 59 provided with a pair of pins 61 adapted alternatelyto engage the teeth of the escapement whee as the clock mechanismoperates. A stop pin 62 is brought into engagement with the arm 63secured to the plunger 64 as the plunger is held in the unoperatedposition thereof by the spring member 65 prior to the launching of themine. When the clock hydrostat operates, the arm 63 is moved out ofengagement with the stop pin 62 by the hydrostat thereby setting theclock in operation and causing the cam member 66 thereof to be rotateduntil the end portion 67 of theslot 68 within the cam member engages thefixed pin 69 thereby preventing further movement of the cam member andbringing the clock mechanism to rest. The movement of the cam memberfificauses the cam contacts A and B to be closed when a predetermined timesuch, for example, as twenty minutes has elapsed after the clockhydrostat is operated, and the cam C contacts to be closed when anadditional period of time has elapsed such, for example, as twenty-fiveminutes after the A and B cam contacts close. The cam contacts A, B andC remain closed by reason of the cam being brought to rest as the end 67of the slot therein engages the fixed pin Referring now to Fig. 2 thereis shown thereon an annular member 71 having a pair of substantiallyhemispherical covers 72 and 73 secured thereto as by the bolts 74 andnuts 75 thereby to enclose the mine firing mechanism and prevent damageand injury thereto. a pair of gaskets 76 and 77 being arranged betweenthe annular member 71 of the covers 72 and 73 respectively whereby themine firing mechanism is hermetically sealed within the covers. Theannular member 71 is provided with two bearing supports diametricallydisposed thereon upon which is pivotally mounted as by the ball bearings78 the gimbal ring 79. The ring 79 is provided with a pair of recessedportions therein respectively enclosed by a pair of circular plates 81within which are arranged the ball bearings 82, Figs. 7 and 8, the ballbearings being fitted to the bearing supports 83 secured to the casing184 as by the screws 85, the casing thus being suspended by gimbals andmaintained in a vertical position by reason of a counterweight 86secured to the lower side thereof in any suitable manner as by thescrews 87.

Coaxial with the ball bearings 78 are the insulated pins '88 having arounded or pointed end for establishing electrical connection with .thecontact springs 89 se ured to the annular member 79 as by the screws 91and insulated there-from in any well known manner such, for example,asby the insulating sleeves and washers illustrated. A second pair ofinsulated contact springs 92 are in electrical connection with thesprings 89 by the conductors varieties thereof. Also, if desired, thepad 44 may be re- 93 and adapted to engage the insulated pins 94, Figs.7

and 8, at the rounded or pointed ends thereof whereby no appreciableresistance tothe free movement of the gimbals is introduced by theengagement of the springs 89 and 92 with their respective contact pins.The contact pins 94, it will be understood, are'coaxial with the ballbearings 82 and insulated therefrom generally in the manner of the pins88. The bearing supports 83 are each provided with an aperture orrecessed portion within which is arranged the conductors 95 and 96respectively secured at one end thereof to the insulating pins 94thereby providing an arrangement in which two external circuits areadapted to be established to the mine firing and Iantude setting andcontrol mechanism through the gimbal bearing supports indicatedgenerally at GCl and GC2, Fig. 15, the common or ground circuit beingestablished through the ball bearings by way of one of the conductorswithin the cable 49 secured to the annular member 71 as at 97, Fig. 1,adjacent one of the insulated pins 88, the external circuit to the otherof the insulated pins 88 being established by way of a conductor as at98 arranged within a recessed portion along the outer periphery of theannular member 71 and preferably secured thereto as by the straps 99 andscrews '101.

The magnetic needle or element of Figs. 7 and 8 comprises two parallelmagnetized steel bars 102 preferably tapered from the central portiontoward the ends thereof and having an aperture in the center portionwithin which is disposed a shaft 103, a metal strip 1040f aluminum orother light non-magnetic material being provided with projectingportions or tabs 105 adapted to engage complementary recessed portionsof the magnetic bars 102 and maintain the bars in parallel lockedengagement with each other, the metal strip 104 also serving as an airbafiie to prevent sudden movement of the magnetic element within the airchamber 106. The supports 83 have their inner ends curved to impede theflow of air past the ends of the baffie plate or strip 104 as themagnetic element is moved angularly within the air chamber and apartition or baffie member 107 secured preferably to the upper portionof the air chamber impedes the flow of air at one end of the upper partof the air chamber to the other end thereof as the magnetic element ismoved angularly within the air chamber 106.

The bushing members 108 are spun or otherwise secured to the magneticbars 102 and clamped to the shaft 103 by the rivets 109 and clampingplate 111,'Figs. 4 and- 9. The shaft 103 is provided with an insulatingbushing 1112 upon which is mounted the contact arm 1'13 as-"by thescrews 114, Fig. 6. The contact arm has a turned up portion 115 to whichthe contact member 116 is secured as by the nuts 117. The contactmember116 is prefer-- ably tapered or rounded at each end thereof and adaptedto engage the contact springs 1-18 and 119, as the case may be, as themagnetized bar moves into the tiring position thereof by a change in themagnetic field adjacent the bar. The contact spring 118 is adapted torest against the stop member 121 when the contact arm 113 is in thearmed position. Prior to the launching of the min'qhowever, the contactmember 1 16 is maintained in continuous engagement with the contactspring 118 by a fuse member as will more clearly appear as thedescription proceeds. The contact spring 118 and stop member 121 areclamped to a support 122 secured to an insulating member 123 of materialsuitable for the purpose such, for example, as Bakelite, hard rubber andthe like in any suitable manner as by the rivets or screws 124. Themember 122 is provided with a screw terminal 125 for establishing anexternal circuit thereto. The arm 126 secured to the insulating member123 as at 127 is provided for adjusting the position of the spring 11 8with respect to the contact member 116, the arm 126 and insulatingmember being pivotally supported by the screw 128 haing a washer 129thereon about which the spring assembly is adapted to be moved. The endof the arm 126 is provided with a bent over portion 131 adapted to beengaged by the adjusting screws 132 threaded within the support 133secured to.

the plate 134 as by the screws 135, the nuts 136 being employed tomaintain the adjusting screws in the adjusted position thereof.

In a similar manner the contact spring 119 and stop member 130 aresupported by an insulating member 137 secured to the adjusting arm 1-38and pivotally supported by the screw 139 having a washer 141 thereon. Ascrew 142 in electrical circuit with the spring 119 is provided forconnection to an electrical conductor. The end of the arm 138 is formedas at 143 to a shape suitable for engagement with the adjusting screws1'44 threaded within the bracket 145 secured to the plate 134 as by thescrews 146, a pair of nuts 147 being employed to maintain the arm 138 inany of its adjusted positions. An arrangement is thus provided in whichthe degree of separation between the contact member 116 and the contactsprings 118 and 119 may be varied at will by adjustment of the screws13-2 and 144 whereby the degree of angular movement of the firingelement including the magnetized bars 102 in either direction from thearmed position thereof necessary to tire the mine may be set to anydesired angle.

The firing or contact arm 113 has connected thereto a biasing spring 148for yieldably setting the magnetic element to a predeterminedsensitivity by the latitude setting mechanism employed with the presentinvention, the biasing springalso being employed for establishing acircuit connection to the firing contact element 116. The shaft 103,Fig. 9, is formed to a V-shaped knife edge 149 at the ends thereof forengagement with the V-shaped jewel bearings 151 set within the threadedbearing screws 152 slideably mounted within the mounting plates 153 and154 aflixed to the sides of the air chamber, a pin such as the pin 155,Fig. 14, passing through each of the plates 1'53 and 154 in the mannerillustrated sufliciently to engage a slot 156 in each of the bearingscrews to prevent rotation thereof as the screws are adjustably clampedin position against the mounting plates 153 and 1 54 by the nuts 157threaded thereon.

A movable member 158 pivoted to the air chamber at 159 is provided witha block 161 having a serrated surface 162 thereon adapted to engage acomplementary serrated surface on the plate 111 secured to the lowerside of the shaft 103 and raise the shaft thereby to rotate the magneticelement to an initial position in which the con tact member 116 ismaintained in continuous engagement with the spring 118 and the knifeedges are disengaged from their jewel bearings until a predeterminedperiod of time has elapsed after the mine has been launched within abody of water. The shaft 164 having an arm 165 thereon adapted to engagethe member 158 is pivotally mounted to the sides of the air chamber andprovided with a lever arm 166, Figs. 3 and 6, having a clamp 167 at oneend thereof adapted to hold the fuse element 168 and thus maintain theshaft 164 in an operated position and the magnetic element in a positionsuch that the knife edge supports therefor are clear of their bearingsuntil the fuse is operated in response to the operation of the hydrostatcloak, as will more clearly appear as the description procee s.

The member 158 is moved by the spring 169 to the position shown indashed outline on Fig. 7 thereby lowering the shaft 103 such that themagnetic element is in contact with and adapted to be moved about itsjeweled bearing supports. The other end of the fuse element 168 isattached to the fuse block 171 as by the screw 172 and clamping member173. The fuse block 171 is secured to the plate 134 and insulatedtherefrom as by the block of insulating material 174, the fuse blockalso being provided with the terminal screw 175 adapted to receive andclamp an electrical conductor for establishing a circuit connection withthe fuse 168. The arm 166, it will be noted, is preferably of suitableinsulating material such, for example, as material known in the art asBakelite, havlng a clamping member 176 secured thereto adapted to coactwith the complementary member 177 and clamp the arm to the shaft 164 asby the screws 178. The arm 166 is also provided with a projectingportion 179 adapted to be arrested by a back-stop pin 181 secured to theplate 134 and having a flexible conductor 18-2 connected thereto and toa terminal screw 183 on the clamping memher 167 for establishing anelectrical connection between the fuse 168 and the plate 134. The aircore coils 184 and 185 are mounted beneath the air chamber in anysuitable manner as by the screws 186, Fig. 7, each of the coils whenenergized being adapted to maintain the magnetic element in therespective firing position in response to the closure of the firingcontacts, the coils being respectively connected in series with thecontact springs 118 and 119.

The mechanism employed for setting the magnetic element to apredetermined position such that the firing contact 116 thereof isintermediate the contact springs 118 and 119 will best be understood by-reference to Figs. 3,

4 and 5 of the drawings on which is shown, partly in section, thearrangement of parts and instrumentalities employed for mparting apredetermined degree of bias of tension to the biasing spring 148 which,as heretofore stated, is connected at one end thereof to the shaft 103to which the magnetized bars 102 are afiixed. The latitude settingdevice comprises a gear train having an cscapement wheel 187 securedthereto adapted to engage the pins 188 alternately as the escapementwheel operates, the pins 188 being secured to the member 189 supportedby the shaft 191. Also secured to the shaft 191 is an oscillatingmetallic member 192 provided with a counterweight 193 secured thereto asby the screw 194 and normally restrained from movement by the arm 195pivoted at 196, Fig. 4, and normally urged out of engagementwith thearrnt195 by the spring 197, the arm being normally held in therestrained position by "the portion 179 of the lever arm 166 therebyproviding an arrangement in which the lever arm 195 is moved out ofengagement with the member 192 as the fuse 16S, Figs. 3 and' 6, isoperated. A slot 198 is provided within the plate 199 to provide formovement of the arm 195. The plate 199, it will be noted, is secured tothe plate 134 by the studs 201 and electrically insulated therefrom asby the insulating bushings 202, a plurality of nuts 203 being providedfor this purpose. The studs 201 also sup port the plate 153 in spacedrelation with respect to the plates 134 and 199 by reason of the spacingmembers 204 provided therebetween.

The escapement wheel 187 is connected by way of the gears 205 and 206 tothe gear 207 having a ratchet 208, Fig. 5, by means of which the gear207 is adapted to be driven by the gear 209. The gear 209, it will beunderstood, is adapted to rotate about the shaft which supports the gear207 and is urged toward the gear 207 by the spring 211, the gears 207and 209 being held in a predetermined position with respect to theescapement mechanism by the bearing support 212 secured to the plate 199in the manner illustrated on Fig. 5. Afiixed to the .bearing support 212is a plate 213 having a bearing therein for pivotally supporting a shaftupon which the gears 207 and 209 are mounted, a screw 214 and the dowelpins illustrated preferably being employed for maintaining the plate 213in the assembled position. The gear 209 is in engagement with the teeth215 of the spring barrel 216 within which is arranged a spring 217composed preferably of non-magnetic material such, for example, asberyllium copper or Phosphor bronze having one end thereof connected tothe spring barrel and the other end connected to a support 218, Fig. 4.The support 218 is secured to the plate 199 as by the screws 219.

Rotatably mounted on the support 218 is a drum 221 having an aperturetherein within which is threaded a collar 222 in abutting relation withone end of the support 218. There is also provided within the drum 221and collar 222 a shaft 223 having a shoulder at one end thereof inengagement with the collar 222 and locked thereto and to the drum by thenut 224 whereby the drum and shaft 223 are adapted to rotate as a unitabout the support 218. Secured to the shoulder of the shaft 223 is anarm 225 having a flexible conductor 226 connected thereto and a bentover portion 227 to which is affixed as by the screws 228 a plate 229 towhich the biasing spring 148 is secured to the outer end thereof as bythe plate 231 and screw 232. From the foregoing it will be apparent thatthe degree of bias applied by the spring 148 is in accordance with thesetting of the drum.

The drum 221 comprises an internal gear 233 secured thereto as by thescrews 234 and having a pair of stoppins 235 adapted to engage a stud236 secured to the plate 199 thereby to limit the degree of motion ofthe spring 217. Pivotally mounted on the support 218 is an arm 237having a stud 238 thereon to which is pivotally secured a gear 239 inmesh with the internal gear 233' and the teeth 215 of the spring barrel216, the stud 238 extending through an arcuate slot 241 within the plate199 thereby to establish a circuit connection between the arm 237 andthe firing contact member 116 by way of the flexible conductor 226secured thereto in any suitable manner-as by soldering the conductorthereon to the arm 225. The arm 237 is provided with a pawl 242pivotally secured thereto as at 243, a resilient spring member 244 beingadapted to urge the pawl yieldably into engagement with a serrated orknurled surface on the outer periphery of the drum 221. The arm 237 isprovided with a pair of turned up portions 245 and 246 within which oneend of the pawl 242 is arranged. The pawl 242 has secured thereto as bythe screws 247 a fuse clamp 248 to which is secured one end of the fuse249, the fuse clamp being connected to the insulated screw 252 withinthe plate 199 by the flexible conductor 251 secured thereto, the otherend of the flexible conductor being preferably soldered to a terminal onthe fuse clamp in the manner illustrated. The fuse clamp is electricallyinsulated from the pawl 242 by suitable insulating washers, the pawlbeing tapered at the outer end thereof to engage the trip switchmechanism with the pawl in the initial locked position at the portion253 thereof thereby to maintain the associated trip switch contacts inengagement with each other until the fuse 249 has operated. The oppositeend of the fuse 249 is clamped by the screw 25,4 and clamping plate "255secured to the metal strip 256 having a terminal 257 thereon forestablishing a circuit connection to the fuse 249. The metal strip orplate 256 is secured in any suitable manner as by riveting to thesupport 258 of insulating material secured to the plate 199 as by thescrews 260, a suitable spacing member being preferably arranged betweenthe support 258 and the plate 199 to bring the fuse 249 into alinedrelation with respect to the plate 199. The bent up portion 246 of thearm 237, it will be noted, is maintained in engagementwith the support258 by the fuse member 249 until the fuse 249 is blown by a flow ofcurrent therethrough, as will more clearly appear as the descriptionproceeds. When this occurs the pawl 242 engages the outer periphery ofthe drum 221 which, as heretofore stated, is preferably knurled orserrated, thereby to insure a locking engagement between the pawl andthe drum as the pawl is actuated by the spring member 244.

The arm 237 is provided with an electrical contact 259 adapted to engagecontact screw 261 when the arm moves to the final s'et position shown indashed outline on Fig. 3. The contact screw 261 is clamped by the stud262 passing through an arcuate slot 263 within the plate 199 andinsulated therefrom by the spacing member 264 composed of materialsuitable for the purpose such, for example, as Bakelite, hard rubber orthe like.

The stud 262 is clamped in any desired position by the nut 265, Fig. 4,thereon in engagement with a conductor 266'thereby to establish anexternal circuit connection to thecontact screw'261, an insulatingwasher 267 being arranged between the conductor 266 and the mountingplate 199 thereby to insulate the conductor and nut from the plate. Theplate 199 is also provided with a plurality of scale divisions orcalibration marks 268 adjacent the aperture 263 therein whereby thecontact screw 261 may be given any desired setting in accordance with apredetermined degree of sensitivity at which the device is to be set.The plates 134 and 269 comprising the casing 84 are extended downwardbeyond the spacing plate 271 and provided with a plate 272 securedthereto as by the screws 273 thereby to provide a compartment 274 withinwhich is arranged a counterbalance weight 275 adapted to be shiftedlaterally in either direction by the threaded studs 276 and 277journaled within the plates 134 and 269. The studs 276 and 277 arepreferably slotted at one end thereof to enable the studs to be adjustedand each provided with a nut 278 to maintain the counterbalance weight275 in the adjusted position thereof such I that the firing controlmechanism including the pendulum device 312, hereinafter referred to asPM, secured thereto,

assumes a vertical position when the mine is at rest by reason of thegimbal mounting provided therefor.

There is secured to the mounting plate 199 as by the screws 279 avsupport 281 having a pair of electromagnets 282 in proximate relationwith respect to the member 192 and adapted to attract the enlarged ironportion of the member 192 thereto and arrest the operation of thelatitude setting mechanism during the time that the electromagnets areenergized. For convenience in describing the operation of the system ofthe present invention, the electromagnets 282 are hereinafter identifiedby the designation EL.

Secured to the plate 199 as by the screws 283 and 284 and nuts 285threaded thereon are a pair of trip switches T81 and TS2, Figs. 10 to13, indicated generally by the numeral 286, a plate or cover 287 beingprovided to enclose and protect the mechanism of the switch TS1. Aplurality of washers 288 are preferably provided between the screws 283and 284 and the cover 287 to hold the switch assembly securely inposition against the plate 199. Referring now particularly to Fig. 12 onwhich is shown a view of. the mechanism of the switch TS1, a casing 289of suitable insulating material such as molded Bakelite, hard rubber orthe like, is provided with a recessed portion therein within which aredisposed the contact springs 291 and 292 normally held in engagementwith each other by the rocker arm or hammer 293 pivotally mounted on thescrew 284 and retained in the operated position by the tapered end 253of the pawl member 242 until the fuse 249 operates. As the fuse 249operates, the tapered end 253 of the pawl is moved out of engagementwith the projection 294 of the rocker arm by the spring 244, Fig. 3,thereby causing the contact spring 291 to move out of engagement withthe spring 292 and thus interrupt the circuit to a control relay as willhereinafter more clearly appear as the description proceeds.

The trip switch T82 is generally similar in construction to the switchTSl, the switch TS2 comprising a rocker arm 295 pivoted about the screw284 and having a projecting portion 296 thereon adapted to be operatedby the tapered end of the arm 237 until the arm has been moved by thelatitude setting mechanism away from the initial locked positionthereof. The operation of the rocker arm 295 to the released positionthereof causes the contact spring 297 to be moved into engagement withthe contact spring 298 thereby closing a circuit to the air coil 185,Fig. 15. Three terminals 299 are provided for establishing an externalelectrical circuit connection to the trip switches, the circuits beingextended from the terminals by suitable conductors to the contactsprings 292, 297 and 298 of the trip switches, the spring 291 beingconnected by the flexible conductor 301 to the screw terminal 302 on theplate 199. Secured to the shaft 103 as by the screw 303 is a hub orcollar 304 having a plurality of radially extending arms 305, 306 and307 thereon upon which are respectively mounted the ad: justable weights308, 309 and 311, Figs. 4 and 9 thereby to apply a small mechanical biasto the shaft 103 variably in accordance with the settings of the weights309 and 311, the speed of response of the magnetic bars 102 to apredetermined change in the magnetic field adjacent thereto beingcontrolled by the setting of the weight 308. The weights 309 and 311, itwill be noted, coact with the biasing spring 148 in applying thesensitivity adjustment to the magnetic bars whereby the sensitivity ofthe bars is controlled by the force of gravity on the weights 309 and311 and the sensitivity setting of the biasing spring.

The pendulum employed with the system of the present invention issubstantially identical with the pendultun disclosed on the aforesaidapplication of James B. Glennon and Chester M. Van Atta, Serial No.395,230, filed May 26, 1941, for Firing Mechanism For A Submarine Mine,the pendulum comprising, among other elements, a tublular member 312secured to the plate 269 by the supports 313 and screws 314, thependulum being maintained in a predetermined position with respect -tothe support by reason of the clamping screws 315 provided within thesupport. The pendulum mechanism comprises a bob pivotally supported fromthe screw member 316 and electrically insulated from the sleeve 312 asby the bushing 317 and secured thereto by the nut 318, a pair of nuts319 being provided for establishing an external electrical connection tothe pendulum. The pendulum includes an electrical contact arrangedwithin an annular contact member connected to the terminal screw 321passing through the tubular member 312 and insulated therefrom as by thebushings 322, the screw 321 being maintained in the assembled positionby reason ofthe nut 323 threaded thereon, a nut 324 and washer beingalso provided on the screw, 321 for establishing an external, electricalconnection to the annular contact member within the pendulum. The lowerend of the pendulum is preferably enclosed by a suitable cap 325 securedthereto in any suitable manner as by threading the parts togetherthereby to exclude moisture and foreign matter from the interior of thependulum casing. A structure is thus provided in which the pendulumcloses a circuit between the screw terminals 316 and 321 whenever thependulum is moved from the vertical position thereof or suddenlydisplaced from an initial position as by the shock received from acountermining operation.

Secured to the plate 269 in any suitable manner as by the support 326 isa relay 327 hereinafter referred to as R having an electromagnet 328with a core of ferromagnetic material thereiri such, for example, asiron in substantial alinement with the shaft 103 of the magnetic elementsuch that the field set up in response to the energization of theelectromagnet is substantially in coaxial alinement with the axis of thepivoted magnetic bars 102 and for this reason the vertical component ofthe magnetic field acting on the electromagnetic bars is substantiallyunchanged when the relay operates. The relay R is also provided with apair of contact springs 329 adapted to be electrically connectedtogether as armature 331 moves to the operated position thereof inresponse to the energization of the electromagnet 328. The armature isnormally retained in the unoperated position with the contact springs329 thereof electrically disengaged by the adjustable retractile spring332 connected thereto. Secured to the lower portion of the support 326as by the screws 333 is preferably mounted a counterweight 334 for thereason that the relay 327 illustrated is of the type in which the partsthereof are of relatively light weight and it will, of course, beunderstood that by the selection of a heavier relay or by slightrearrangement of the parts or design of the structure supported by thegimbals, the counterweight 334 may be omitted.

Secured to the plate 272 as by the screws 335 is a time delay relaymechanism 336 hereinafter referred to as TD1 adapted to operate thecontacts thereof when an energizing current has flowed through the relaywinding for a predetermined period of time. As clearly shown in Fig. 15relay TD1 comprises a rotatable armature 337 normally urged against aback-stop 338 by a retractile spring 339 secured thereto. The armature337 is adapted to be actuated quickly by the energization of theelectromagnet to the operated position thereof and return slowly to thereleased position by reason of a clockwork escapement mechanismconnected thereto as is well known in devices of this character. As therelay operates, the armature 337 thereof causes a contact spring to bemoved away from a normally engaged contact and into engagement with asecond contact thereby to control certain circuit functions of thesystem in response to the operation of the pendulum as will more clearlyappear as the description proceeds. The external circuit connections tothe relay are established by way of the connecting screws 341, Figs. 7-and 8, and terminal connections 342 provided thereon. Preferably, thoughnot necessarily, the relay mechanism is enclosed within a cover orcasing indicated generally by the numeral 343 for preventing dirt ormoisture from coming into contact with the relay clock mechanism andcontact elements controlled thereby during the construction and assemblyof the device.

The operation of the system will now be described. Let it be assumed, byway of example, that the fuse-elements 168 and 249, Fig. 15, have beenplacedin position, the spring motors of the clock timing mechanism TMand the latitude setting mechanism have been wound, the detonator 21 isconnected, an explosive charge has been placed within the mine casingand the mine has been sealed and launched within a body of wateradjacent the path of travel of a vessel. When the mine has descended. toa predetermined depth of submersion within the water, the pressure ofthe water causes the extender and clock hydrostats to operate therebymoving the detonator 21 into operative position with respect to thebooster charge 22, the clock hydrostat causing the movement of theplunger 64 to withdraw the arm 63 out of engagement with the stop pin 62thereby setting the clock timing mechanism TM in operation. Whereas inthe illustrativeembodiment of the invention shown on the drawings twohydrostats are employed for extending the detonator within the boostercharge and setting the clock timing mechanism in operation it will, ofcourse, be understood that, if desired, a single hydrostat may beprovided for this dual purpose.

When a periodof time such, for example, as twenty minutes has elapsedafter the clock TM has been started, the cam contacts A and B thereofare closed by the cam member 66 thereby completing a circuit from groundat the cam contacts B by way of conductor 344 to the negative terminalof battery BA from whence the circuit is continued by way of thepositive terminal of battery BA, conductor 345, contacts of cam A,conductor 346, gimbal contacts G01, conductor 347, contacts 348 of thetime delay mechanism TD1, conductor 349, fuse element 168 and thence toground at 351 thereby causing the fuse element 168 to blow and interruptthe circuit just described. The operation of the fuse element alsocauses shaft 164 and certain of the control mechanism associatedtherewith illustrated graphically by the member 352 to rotate by theaction of spring 169 sufiiciently to disengage the member 192 therebyallowing the member 192 to oscillate and set the latitude settingmechanism into operation. As shaft 164 is rotated, the arm 165 thereofcauses the member 158 to pivot about the bearing 159 and thereby unlockthe magnetic element comprising the magnetized bars 102 by moving theshaft 103 thereof into engagement with its jeweled supports. Themagnetic detecting element is now in readiness to be actuated by thelatitude setting mechanism.

The operation of the latitude setting mechanism will best be understoodby consideration of Fig. 3 of the drawings on which is clearly shown thespring barrel 216 urged by the spring 217 in a clockwise direction. Whenthe member 192 begins to oscillate, the escapement mechanism allows thespring barrel to rotate slowly clockwise and thereby cause the gear 239pivoted to the stud 238 on the arm 237 to rotate in a counterclockwisedirection. The gear 239 is meshed internally with the gear 233 connectedto the drum 221 thereby causing the drum and the shaft 223 connectedthereto to be moved in a counterclockwise direction. The other end ofthe shaft 223 is connected to the arm 225, Figs. 4 and 9, therebycausing the arm 225 to be moved integrally with the drum in acounterclockwise direction and carry with it the outer end of thebiasing spring 148 secured to the bent end 227 of the arm. As the drum221 continues to move in a counterclockwise direction the bias appliedby spring 148 to the shaft 103 is changed sufficiently to cause themagnetic detecting element to be moved angularly until the firingcontact 116 thereof is brought into engagement with the contact spring119.

When this occurs a circuit is closed from ground at contacts B of thetiming mechanism TM by way of conductor 344, battery BA, conductor 345,contacts A of the timing mechanism, conductor 346, gimbal contacts (3C1,conductor 347, contacts 348 of the time delay mechanism TD1, conductor349, air core coil 186, contact spring 119 and firing contacts 116,conductor 353, contact springs 291 and 292 of the trip switch TS1,conductor 354, winding of relay R and thence to ground thereby causingrelay R to operate. As armature 331 of relay R moves into engagementwith its make contact a circuit is closed from ground at cam B contactsof the timing mechanism TM, conductor 344, battery BA, condoctor 345,cam A contacts, conductor 346, gimbal contacts GCl, conductor 347,contacts 348 of time delay mechanism TD1, conductor 349, make contactand armature 331 of relay R, conductor 355, fuse element 249 and thenceto groundat 356thereby causing the fuse 249 to blow and release the pawl242. As the pawl 242 moves into locked engagement with the serratedouter periphery of the drum 221, the drum is locked to the arm 237thereby preventing additional rotative movement of the drum with respectto the arm. The gear 239, Fig. 3, is thus locked to the arm by the drumand pawl there-by preventing further additional movement of the gear 239with respect to the arm 237. The spring barrel 216, it will be recalled,is moved continuously in a clockwise direction and by reason of thelocked relation of the gear 239 with respect to the drum 221, the drumis also locked to the spring barrel and moves integrally therewith in aclockwise direction, the direction of movement of the drum 221 and thearm 225 connected thereto now being reversed. As the pawl 242 moves intolocking engagement with the drum 221 the tapered end 253 thereof quicklymoves away from the projecting portion 294 of the hammer 293 of the tripswitch T S1 thereby releasing the hammer and interrupting the circuit tothe air core coil 184 and relay Rand causing relay R to release. Asarmature 331 of relay R moves away from its make contact, battery isremoved from conductor 355.

As the spring 217 continues to unwind, the bias applied by the spring148 to the shaft 103 is changed in a direction to cause the firingcontact 116 to be moved away from the contact spring 119. The movementof the tapered end of the arm 237 away from its initial locked positionreleases the hammer 295 of the trip switch TS2 thereby causing spring297 thereof to be moved into engagement with contact spring 298 therebycompleting a circuit from battery on conductor 349 by way of the closedcontacts of trip switch TS2, conductor 357 to one end of the winding ofthe air core coil from whence the circuit is continued by way ofconductor 358 to contact spring 118 of the firing mechanism. Thelatitude setting arm 237 continues to rotate in a clockwise directionuntil the arm is arrested by the contact 259 thereof moving intoengagement with the adjustable contact screw 261 thereby causing thelatitude setting mechanism to be brought to rest with the magnetizedelement thereof set in an armed position such that the firing contactelement 116 is intermediate the contact springs 118 and 119, themagnetic element and firing contact 1.16 being yieldably maintained inthis position by the biasing spring 143. The mine is now in a conditionsuch that the firing contact 116 is adapted to be moved upward ordownward into engagement with the contact springs 118 and 119respectively in accordance with a positive or negative variation in theearths magnetic field adjacent the magnetized element.

When a predetermined period of time has elapsed such, for example, astwenty-five minutes after cam contacts A and B close, the cam contacts Care closed by the clock timing mechanism TM thereby applying ground atcam 13 contacts by way of conductor 344, cam C contacts, conductor 359,and thence to contact spring 361 and one end of the winding of the timedelay mechanism TD2. The mine is now in an armed condition. When the end67 of the slot 68 within the cam member 66 engages the stop pin 69 theclock timing mechanism TM is brought to rest with the cam contacts A, Band C thereof maintained in a closed condition by the cam 66.

The time delay mechanism TD2 is generally similar to the time delaymechanism TD1 in which a rotatable armature is caused to be actuated byenergization of an electromagnet thereby operating a clock escapementmechanism or similar device adapted to retard the movement of thearmature sufiiciently to allow a predetermined period of timesuch, forexample, as two and one-half seconds to expire after the electromagnethas been energized before the contact spring 361 is moved into circuitclosing position by the rotatable armature thereby to delay the firingof the detonating device 21 for a period of time greater than thatrequired for the operation of the anti-countermining feature which willbe described with particularity as the description proceeds.Furthermore, by employing a time delay mechanism TD2 intermediate thefiring contacts and the detonating device 21 the firing of the detonatoris delayed thereby causing the explosion to occur more nearly toward thestern of the passing vessel.

The operation of the system caused by a disturbance of the mine such,for example, as may result from countermining, will now be described.When the mine is suddenly moved or disturbed the pendulum PM, Fig. 15,moves relative to the contacts thereof and applies ground to conductor362, winding of time delay relay TD1 from whence the circuit iscontinued by way of conductor 349, contacts 348 of the timing mechanismTD1, conductor 347, gimbal contacts GCl, conductor 346, cam contacts Aof the timing mechanism TM, conductor 345 to the positive terminal ofbattery BA thereby causing the time delay relay TD1 to operate thearmature 337 thereof quickly to the operated position. As armature 337operates, the contacts 348 are disengaged thereby interrupting thecircuit of the winding of time delay mechanism TD1. As armature 337 ofthe time delay mechanism TD1 moves toward the unoperated positionthereof, the clock escapement mechanism thereof is caused to operate andretard the movement of the armature such that the contacts 348 aremaintained open for a suitable period of time such, for example, asthirty-five seconds after the operating circuit to the electromagnet ofthe time delay mechanism TD1 is interrupted.

As contact spring 363 moves away from contact 348 into engagement withcontact 364, a circuit is closed from ground at cam B of the timingmechanism TM, conductor 344, battery BA, conductor 345, cam convtacts Aof the timing mechanism TM, conductor 346,

gimbal contacts GCI, conductor 347, contact spring 363,

contact 364, conductor 365, electromagnet EL and thence to groundthereby energizing the electromagnet EL and causing the oscillatingmember 192 to be attracted there-' to and arrest the latitude settingmechanism in the event that the pendulum PM operated while the. latitudesetting operation was in progress. In the event that the sensitivitysetting of the magnetized element 102 has been completed theenergization of the electromagnet EL is without effect. As contactspring 363 moves away from contact 348 in response to the operation ofarmature 337, battery is removed from conductor 349 whereby the air corecoil 186 and, in the event that the trip switch TS2 had operated, theair core coil 185 are rendered ineffective to maintain the firingcontacts in a closed position in the event that the shock or pressureimpulse received by the mine had been suflicient to cause the firingcontacts to be closed.

When a predetermined period of time has elapsed after the pendulumcontacts are restored to their initial open position, armature 337 movesaway from the operated position sufficiently to disengage contact spring363 from contact 364 thereby deenergizing the electromagnet EL. Ascontact spring 363 engages the contact 348, battery is again applied toconductor 349 and the mine is again in an armed condition. In the eventthat the firing contacts 116 should be moved to closed position by acountermining operation before contact 348 of the time delay mechanismTDl is disengaged from contact spring 363, a circuit is closed fromground at cam B of the timing clock TM, conductor 344, battery BA,conductor 345, cam A, conductor 346, gimbal contacts GCI, conductor 347,contact spring 363 and contact 348 of the time delay mechanism TDl,conductor 349 and thence by way of the hold-on coils 184 or 185, as thecase may be, the circuit of the hold-on coil 185 including the contactsof the trip switch TSZ, closed contacts 259 and 261, conductor 365,gimbal contacts 602, conductor 366, winding of the time delay mechanismTD2, conductor 359, contact C of the timing clock TM, conductor 344,contact B of the timing clock and thence to ground thereby energizingthe winding of the time delay mechanism TD2 in the event that thecountermining operation took place after a period of time has elapsedsufficient to allow contact C of the timing mechanism TM to close.

Armature 337 of the time delay mechanism TDl, it will be recalled, movesquickly to the operated position thereby disengaging contact spring 363from contact 348 before the armature of relay TD2 has moved to a circuitclosing position such that contact spring 361 thereof engages its makecontact and an arrangement is thus provided in which the operatingcircuit of the time delay mechanism TD2 is invariably interrupted priorto the closing of the contacts 361 thereof when a countermining impulseor wave of pressure is received by the mine. By providing a relativelylong period of time delay within the timing mechanism TD1 before thecircuit to the hold-on coils 185 and 184 is again completed, sufficienttime is allowed for the magnetic element or bars 102 to assume a stateof rest with the firing contact 116 thereof intermediate the contacts118 and 119 before the firing circuit is again made effective.

Furthermore, by arresting the latitude setting mechanism whenever themine is disturbed as the result of a countermining operation in theevent that the pendulum contacts are closed during movement of themagnetic element 102 from the initial locked position to the armedposition, the degree of relaxation of the biasing spring 148 necessaryto bring the contact member 116 into closed position with the contactspring 119 thereby to operate relay R and blow the fuse element 249 isthus invariably controlled by the azimuth position of the magneticelement which, it will be recalled, rotates in a vertical plane and thelatitude of the location within which the mine is laid. The tension ofthe spring 148 is gradually increased after the contact element 116 hasbeen brought into engagement with the contact spring 119 until thelatitude setting arm 237 has moved to a predetermined angle of rotationand been brought to rest by the adjustable contact screw 261. Themagnetic element is thus given a predetermined sensitivity settingregardless of countermining operations that may occur during theoperation of the latitude setting mechanism.

Should the pendulum PM operate afterv the latitude setting arm 237hasbeen released by the fuse element 249, the operation of theelectromagnet EL causes the latitude setting mechanism to be arrestedthereby preventing the engagement of the contact 259 of the arm 237 withthe adjustable contact 261 until a predetermined period of time haselapsed after the pendulum has subsided sufiiciently for the contactsthereof to remain continuously disengaged. When this occursthe operatecircuit for the time delay device TD2 is thus maintained open atcontacts 259 and 261 and additionally interrupted at contact 348 of thetime delay device TDI and contact C of the timing clock TM.

Let it now be assumed that a change occurs in the magnetic fieldadjacent the magnetic element such,. for example, as may be caused by avessel approaching within the vicinity of the mine, sufiicient to causethe firing contact element 116 to be moved into engagement'with contactspring 119. When this occurs a circuit is closed from ground at cam B ofthe clock mechanism TM, conductor 344, battery BA, conductor 345, camcontacts A of the clock mechanism, conductor 346, gimbal contacts GCl,conductor 347, contact springs 363 and contact 348 of the time delaymechanism TD1, conductor 349, air core hold-on coil 186, contact spring119, firing contact element 116 and the contact 259 of arm 237, contact261, conductor 365, gimbal contacts GC2, conductor 366, winding of timedelay mechanism TD2, conductor 359, cam C of the clock mechanism TM,conductor 344 and thence to ground at cam B of the clock mechanismthereby causing the time delay mechanism TD2 to attract the armaturethereof. The energization of the hold-on coil 184 over the circuit justdescribed maintains the firing contact 116 in continuous engagement withthe contact spring 119 thereby maintaining a fiow of electrical currentthrough the winding of the time delay mechanism TD2. When apredetermined period of time has elapsed after the firing contacts closesuch, for example, as two and one-half seconds contact spring 361 oftime delay mechanism TD2 engages the make contact thereof therebyclosing a circuit from positive terminal of battery BA, conductor 345,contact A of the clock mechanism, conductor 346, detonating device 21,conductor 367, make contact and contact spring 361 of time delaymechanism TD2, conductor 359, cam C of clock mechanism TM, conductor 344and thence to the negative terminal of battery BA thereby causing thedetonator to operate and fire the mine.

In the event that the approaching vessel caused a change in the magneticfield adjacent the mine in a direction and of strength suflicient tocause the contact element 116 to be moved into engagement with contact118, the time delay mechanism TD2 will operate on a circuit includingcontact spring 118, hold-on coil 185, conductor 357 and the contacts oftrip switch TSZ thereby energizing the hold-on coil 185 and maintainingthe contact element 116 in continuous engagement with con.- tact spring118 until the mine is fired by movement of the contact spring 361 of thetime delay mechanism TD2 into engagement with its make contact thereof.

Whereas in the illustrated embodiment of the invention the time delaydevices TD1 and TD2 have been shown as electromagnetically operated byclock mechanisms, it will be understood that this is by way ofillustration only as various other electro-responsive delay devicescomprising a dash-pot mechanism and other time delay means suitable forthe purpose may be employed.

It will be understood that whenever a change in the magnetic field ofrelatively short duration is received such, for example, as a changeproduced by certain countermining operations, the magnetic element 102is caused to close the firing contacts thereof ballistically and whenthis condition occurs the contacts 116 and 118 or 119, as the case maybe, are opened by the rebound of the magnetic element and the firing armregardless of the energized condition of the associated air core hold-oncoils. The magnetic element is thus prevented from looking in the firingposition when short magnetic pulses are received thereby preventing theoperation of the time delay device TD2 and rendering the mine immune tothis type of mine sweeping operations.

Briefly stated in summary the present invention contemplates theprovision of a new and improved magnetic influence mine in which meansare provided for arming the mine when a predetermined period of time haselapsed after the mine has been launched within a body of water,

for releasing the magnetized field sensing device thereof andautomatically setting the magnetic sensing device to a predeterminedsensitivity or setting such that the firing element thereof is broughtto rest yieldably intermediate a pair of contact elements such that themine is adapted to be fired in response to a predetermined change ofeither polarity in the magnetic field adjacent thereto, the mechanismalso comprising means for preventing the premature explosion of the mineas the result of countermining or mine sweeping operations. In itsbroader aspects the present invention provides means for automaticallysetting a magnetized element yieldably in a predetermined position suchthat the movement of the element in either direction from thepredetermined setting thereof in response to an increase or decrease inthe intensity or a change in any direction in the lines of forcecomposing the magnetic field adjacent thereto is sufiicient to cause themine to fire.

While the invention has been described with particularity as to onepreferred embodiment of a combination of mechanisms and of each of thevarious elements of the combination, it is to be understood that thishas been done for purposes of disclosure and that various changes andmodifications may be readily apparent to those skilled in the art, afterunderstanding the invention herein disclosed, and that the termsemployed in the claims are, therefore, to be considered as words ofdescription rather than of limitation.

The invention herein described and claimed may be manufactured by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In a marine mine of the character disclosed, a mine firing controlmechanism comprising a magnetic dip needle, means including a shaft forpivotally supporting said clip needle for rotative movement about ahorizontal axis, a firing contact connected to said shaft and adapted tobe moved to difierent positions in accordance with the degree ofrotation of the dip needle, a pair of contact elements arranged withinthe path of travel of said firing contact and adapted to be engagedselectively thereby, means for yieldably setting the firing contactintermediate said contact elements after the mine has been launchedwithin a body of water, a firing circuit, and means for closing saidfiring circuit when said firing contact has engaged either of saidcontact elements in response to a predetermined change in the magneticfield adjacent the dip needle.

2. In a submarine mine adapted to be laid on the bed of a body of water,a mine firing control mechanism comprising a magnetized bar adapted tobe moved angularly about a horizontal axis, a firing contact operativelyconnected to said magnetized bar and movable therewith, a pair ofcontact elements arranged on opposite sides of said firing contact andadapted to be engaged selectively thereby when the magnetized bar hasmoved through a predetermined angle of rotation, at source of electricalpower, a pair of coils respectively connected to each of said contactelements and to said source of electrical power and adapted to urge themagnetic bar in a direction to maintain the firing contact in continuousengagement with the associated contact element as the coils areselectively energized, an electro-responsive time delay mechanismoperatively connected to said firing contact and adapted to becontrolled thereby, an explosive charge, electro-responsive means fordetonating said explosive charge, and means including a pair of contactsadapted to be closed by said electro-responsive mechanism in timedelayed relation with respect to the engagement of said firing contactswith either of said contact elements for causing said explosive chargeto be fired by said detonating means.

3. In a mine firing mechanism of the character dis closed, thecombination of a firing circuit having two branches therein, a pair ofcontact elements respectively associated with said branches, a movablefiring contact arranged intermediate said contact elements and adaptedto engage the contact elements selectively, a pivoted magnetic elementadapted to be actuated by changes in the verticai component of themagnetic field adjacent thereto for controlling the movement of saidfiring contact, means for yieldably setting said magnetic element to anarmed position with the firing contact disengaged from said contactelements, and means responsive to the engagement of said firing contactwith either of said contact elements for closing said firing circuitthrough the associated branch thereof.

4. A mine firing control mechanism of the character disclosed comprisinga magnetized bar pivotally supported for rotative movement about ahorizontal axis, a contact arm operatively connected to said magnetizedbar and rotatable therewith, a pair of contact elements arranged onopposite sides of said arm and adapted to be engaged selectively by thecontact arm when the magnetized bar has moved through a predeterminedangle, means for moving said contact arm into engagement with one ofsaid contact elements, means controlled by said one of said contactelements for reversing the direction of motion of said contact arm, andmeans for bringing said contact arm to rest yieldably at a predeterminedsetting intermediate said pair of contact elements and disengagedtherefrom.

5. A mine firing control device of the character disclosed comprising amagnetized bar pivotally supported for rotation about a horizontal axis,a firing contact operatively connected to said magnetized bar androtatable therewith, a pair of contact elements disposed on oppositesides of said firing contact and adapted to be selectively engagedthereby, means for yieldably setting said firing contact to an armedposition intermediate said contact elements and disengaged therefrom, afiring circuit, means for operatively connecting said firing circuit tosaid firing contact as the contact is yieldably set to said armedposition, and means for closing said firing circuit when a predeterminedperiod of time has elapsed after the firing contact has been moved intoengagement of either of said contact elements by said magnetized bar inresponse to a change in the magnetic field adjacent thereto.

6. A mine firing control device of the character disclosed comprising amagnetized bar pivotally supported for rotative movement about ahorizontal axis, a firing contact operatively connected to saidmagnetized bar and rotatable therewith, a pair of contact elementsarranged on opposite sides of said firing contact and adapted to beselectively engaged thereby, means for yieldably setting said firingcontact to an armed position intermediate said contact elements anddisengaged therefrom, an electroresponsive time delay device, means forconnecting said electro-responsive time delay device to said firingcontact as the contact is yieldably set to said armed position, a firingcircuit including a detonating device operatively connected to saidelectro-responsive device, and means included in said electro-responsivedevice for closing said firing circuit when a predetermined period oftime has elapsed after the electro-responsive device has been operat'edby the firing contact in response to the engagement of the firingcontact with either of said contact elements.

7. In a magnetically controlled mine firing device, the combination of apivoted magnetized element adapted to respond to changes in the verticalcomponent of the earths magnetic field adjacent thereto, means includinga shaft for pivotally supporting said magnetized element for movementabout a horizontal axis, a pair of contact devices, a firing contactsupported by said shaft and operatively connected to said magnetizedelement, means for yieldably actuating said firing contact intoengagement with a predetermined one of said contact devices, meansresponsive to the engagement of the firing contact with saidpredetermined one of said contact devices for moving the firing contactreversely to an armed setting intermediate said pair of contact devices,a source of electrical energy, means for connecting said predeterminedone of said contact devices to said source of electrical energy prior tothe engagement of the firing contact therewith, means for connecting theother of said contact devices to said source of energy subsequent to theengagement of the firing contact with said predetermined one of saidcontact devices, a firing circuit, and means effective when the firingcontact has been moved to said armed setting for causing the firingcircuit to be operatively con nectcd to said source of electrical energyas the firing contact moves into engagement with either of said contactdevices in response to a predetermined change in the magnetic fieldadjacent the magnetized element.

8. In a submarine mine, the combination of a pivoted magnetic needleresponsive to changes in the vertical component of the magnetic fieldadjacent thereto, means for locking said magnetic needle in an initialposition,

means responsive .to the pressure of the water within which the mine isplanted for releasing said needle for pivotal movement about ahorizontal axis, means for yieldably actuating the need; about said axisto a predetermined position thereof, a first pair of contacts .adaptedto be closed as the magnetic needle moves into Said predeterminedposition, means responsive to the closure of said first pair of contacts-for reversing the. direction of movement of the needle about said axis,a contact device adapted to be closed when the needle has moved to ,apredetermined armed position with the first pair of contacts disengagedfrom each other, a second pair of contacts adapted to be closed whensaid magnetic .needle has been moved through a predetermined anglebeyond said armed position, an electro-responsive time delay device,means effective when the contact device has been closed for operatingsaid time delay device in re- ;sponse to the closure of either of saidpairs of contacts by ..said magnetic needle, and means including adetonating device operatively connected-to said electro-responsivedevice for exploding the mine in predetermined time delay relation asthe eiectro-responsive device is operated by either of said pairs ofcontacts.

9. In a mine having an explosive charge therein adapted tdbe laid on thebed of abody of water, a magnetic detecting device pivotally supportedfor rotation .movement above a horizontal axis, .said magnetic device.being-adapted-to be moved in either direction to diii'erent .settingsselectively in accordance with changes in the vertical component ofthemagnetic fieldad acent thereto, a pair or normally opencontactdevices, a firing element operatively connected to said magneticdetecting :device and vadapted to engage the contact devices selectivelyin accordance with the degreeof angular move- 'ment of ,said magneticdevice, means including a resilient member for yieldably setting saidfiring element to an ,armed position intermediate said pair or' contactdevices and disengaged thererrom, a firing circuit adapted to be closedas the firing element .is moved into engagement Withgeither of saidcontact devices .by a predetermined .changein saidmagnetic field, a pairoftn'ormally closed contactsin said firing circuit, a pendulum devicehaving :meansforclosing anelectrical circuit as themine is dis- ,turoed,.and an =eiectro-responsive device controlled by said circuit closingmeans for quic ly disengaging said pairof normally closed contactstherebyto interrupt :said ,tiringcircuitior aiperiod, oftime sutficientforthe firing ..element to be ,broughttorestdn the armed position :-by..saidresilient member.

10.,ln.a. submarine mine adaptedto be.la id :onthe bed of ..a .body of.water, :the combination of a magnetic element having afiringcontactsecured thereto arranged .-.f,Or rotative movement ahoutahorizontal. axis, means for yieldably ..setting said magnetic .elementand .firing con- .tact to.a;predeterminedtarmed position, a,pair ofcon-..taeLeiementsarranged on opposite sides of;said firing contact andadapted .to .be :engaged selectively thereby .in responseto,ra.pre.determined degree ofangularmove- ,ment of .the .magnetic..element in .either direction from said armed, position,,acontroleircuit adapted to.be closed .as .the firing ..contactengages-either of said contact ,ele- .ments, said control.circuitincluding an electro responsive .device .having a pair .ofnormally open contacts :adapted .to he engaged in timedelayq-relationasthe device operates; .a firing ..circuit including adetonating device adapted to be controlledbysaidnormally opencontacts,,apendulumdevice having ,contactmeansadapted to be -,closed as the mineis.disturbed,.,and.means controlled by said contact meansforjnterrupting ,said controhcircuit before the detonatingdeviceisoperatedtby said electroresponsive means and for maintaining thecontrol circuit interruptedfona period of time suflicient totenable saidmagnetic element and firing contact to be restored to said predetermined.armed position.

11. 'In aimagnetic mine adaptedtobearranged on the feed of a ,body ofwater within the. path of travel of a ,vessel, a pivoted magneticelementselectively responsive to changes in the vertical component ofthe magnetic field adjacent thereto, said element having an initialposition, an armed position and two firing positions, a firing circuit,means including a pair of contacts operatively connected to saidmagnetic element and adapted to be engaged selectively when the elementis in either of said firing positions for closing said firing circuit,latitude setting means yieldably connected to said magnetic element forcausing the magnetic element to ;be .moved from said initial position tosaid armed position, means for setting said latitude setting means inoperation, an electro-responsive time delay device having a pair ofnormally closed contacts and a make contact adapted to close as the timedelay device-operates, means including a pendulum device for operatingthe electro- -responsive device as the mine is disturbed, acontrol'circuit adapted to be interrupted as said pair of normallyclosed contacts of the time delay device are disengaged, and meanscontrolled by said make contact for causing the operation of saidlatitude setting means to-be arrested during the movement of themagneticelement from said initial position to said armed position andfor preventing the reoperation of the latitude setting .means until apredetermined period of time has elapsed after the'time delay device hasbeen released.

12. In a mine firing mechanism of the character disclosed, thecombination of a magnetized bar pivotally supported for rotativemovementabout a hori-zontal axis, a contact arm operatively connected to saidmagnetized bar and rotatable therewith, a pair of contact elementsarranged on opposite sides or said contact arm and adapted to be engagedselectively thereby, means including anelastic connection for yieldablysetting said magnetized bar to an armed position with the contact armintermediate said pair of contact elements and disengaged therefrom, atirstcoil-connected to one of said contact elements and adapted to madwith the magnetized bar thereby to urge the contact arm into con-.tinuous engagement with said one of said contact-elements in responseto movement of the arm into circuit closing position therewith, a secondcoil connected to the other of said contact elements adapted to coactwith the magnetized bar and maintain the contact arm in continuousengagement with said other of the contact elements in response to-movement of thearm intoengagement therewith, asource ofelectricalenergy, means for connecting the first-coil'to said source ofelectrical energy, means controlled by the contact arm for connecting:the second coil to said source of electrical-err .ergy as the armengages said one of-said contactlele- ,ments, a firing controlcircuihmeans,forconnectingthe firing control-circuit'to said-contact armin time'delayed relationwith-respect-tothe connection ofthe second'coilto said sourceot electrical energy, a releasable electroresponsivedeviceicontrolled by said-firingcontrol circuit including a pair ofcontacts adaptedtobe engaged when the firing control circuit hasbeentclosed for a predetermined period. of time, detonating meansadapted tobe fired by saidelectro-responsive device as-the contactsthereof are. engaged, and meansincluding a-plurality of circuitconnections-for maintaining a-continuous flow of current through saidelectro-responsive device fora period of time'sufiicient to cause thecontactsthereofto be engaged and-firethedetonating device.

.13. In .a -mine of the character disclosed, a firing control mechanismcomprising a magnetizedelement responsive to small changes in theearthsmagnetic field adjacent thereto, means maintaining-the mine in an uniarmed condition for apredetermi-nedperiod subsequent to the launchingthereof and including a retaining ele- .ment forholding said magneticelement in a firstposi- :tion,-. means for arming said mine andincluding a spring operatively connected to said magnetic element and,adapted to have the tension thereof adjusted to a preselected valueforpositioning saidmagnetic element yield- -ab1y inasecond predeterminedarmed position, means forzadjustingsaidtension in accordance .with thelatitude of the launching position, amine firing circuit, and -meanscontrolled by-saidmagnetizedelement for closing the mine firing circuitwhen the strength of the vertical component of the earths magnetic fieldadjacent thereto is either increased by apredeterminedincrement-orde-,creased by-a predetermined decrement.

14. A mine firing controlmechanism arranged within ,apmagnetic field,said mechanism comprising-a magnetized bar pivotally supported forrotative movement about a horizontal axis, means for applying apredetermined gravitational bias to said magnetized bar, means includinga resilient member adapted to apply a predetermined additional degree ofbias to said magnetized bar, means including a motor for varying thedegree of bias applied by said resilient member, a pair of contactsadapted to be closed when the bias of said resilient member has beenvaried sufficiently to cause the magnetized bar to be moved rotativelyto a predetermined position thereof, an electrical relay adapted to beoperated by said pair of contacts as the magnetized bar moves into saidpredetermined position, a fusible locking device operatively connectedto said relay and adapted to be released as the relay operates, meansincluding a rotatable member controlled by said fusible device forreversely varying the bias applied by said resilient member suflicientlyto disengage said pair of contacts, and means controlled by saidrotatable member for preventing the reoperation of said relay by saidpair of contacts as the contacts are subsequently closed by themagnetized bar in response to a predetermined change in the verticalcomponent of said magnetic field.

15. A firing control mechanism of the character disclosed comprising amagnetic element pivotally supported for rotative movement about ahorizontal axis, a contact arm operatively connected to said. magneticelement and rotatable therewith, a latitude setting mech- I anism havingan elastic connection for yieldably setting said contact arm andmagnetic element to a predetermined armed position, a pair of contactelements adapted to be engaged selectively by said contact arm when themagnetic element has moved through a predetermined angle in eitherdirection from said armed position, a. firing control circuit adapted tobe closed as the contact arm engages either of said contact elements,and means settable at will for varying the degree of rotative movementof said magnetic element and contact arm necessary to close said firingcontrol circuit.

16. A firing control mechanism of the character disclosed comprising amagnetic element pivotally supported for rotative movement about ahorizontal axis. a contact arm operatively connected to said magneticelement and rotatable therewith, a latitude setting mechanism having anelastic connection for yieldably setting said contact arm and magneticelement to a predetermined armed position, a pair of contact elementsadapted to be engaged selectively by said contact arm when the magneticelement has moved through a predetermined angle in either direction fromsaid armed position, a firing circurt, means operatlvely connected tosaid contact arm and responsive to the engagement of the contact armwith either of said contact elements for closing said firing circuit,and means settable at will for varying the degree of rotative movementof said magnetic element and contact arm necessary to operate saidfiring control circuit closing means.

17. A firing control mechanism of the character disclosed comprising amagnetic element pivotally supported for rotative movement about ahorizontal axis, a contact arm operatively connected to said magneticelement and rotatable therewith, means including a resilient member foryieldably setting said magnetic element and contact arm to an armedposition. a pair of contact devices adapted to be engaged by saidcontact arm selectively in accordance with the degree and direction ofmovement of the magnetic element and contact arm from said armedposition. means for controlling the angle of the magnetic element withres ect to a horizontal plane when the magnetic element and contact armare set to said armed position, and means settable at will for varyingthe degree of an ular movement of the contact arm from said armedosition necessary to engage each of said contact devices.

18. A firin mechanism for a submarine mine of the character disclosedcomprising a shaft having a magnetic bar secured thereto. means forpivotally supporting said shaft and bar for rotative movement in avertical plane. a contact arm secured to said shaft and rotatabletherewith. a pair of contacts arran ed within the path of trave of saidcontact arm and adapted to be en aged thereby when the contact arm hasmoved through a pre determined angle. means for vieldably settin saidcontact arm in a predetermined armed position intermediate said pair ofcontacts and disengaged therefrom. means settable at will in accordancewith the latitude at which the device is arranged for causing saidcontact arm to assume said predetermined armed position after the minehas been launched within a body of water, an electroresponsivetime-delay device having a winding, an electric circuit including saidcontacts and said contact arm and said winding whereby the time-delaydevice is energized upon the closing of the circuit, and detonatingmeans controlled by said time-delay device for exploding the mine apredetermined time after said electric circuit is closed.

19. Mine firing apparatus comprising a detonator, a normally open firingcircuit for said detonator, a pivoted magnetic element adapted to bemoved in response to changes in the vertical component of the magneticfield ambient thereto, an arm operatively connected to said element andadapted to move therewith, fuse means arranged within said mine forretaining said element in a first unarmed position for a predeterminedperiod of time after the mine is launched, spring means adapted to havethe tension thereof varied for subsequently setting said elementin apredetermined armed position in accordance with the latitude where themine is launched, means for adjusting said tension, and means carried bysaid arm for closing said firing circuit when said element moves apredetermined distance in either direction from said armed position inresponse to a change in the magnetic field.

20. Mine firing apparatus comprising a detonator, a normally open firingcircuit for said detonator, a pivoted magnetic element adapted to bemoved in response to changes in the vertical component of the magneticfield ambient thereto, an arm operatively connected to said element andadapted to move therewith, means arranged 'within said mine forretaining said element in a first unarmed position for a predeterminedperiod of time after the mine is launched, means controlled by saidretaining means for subsequently setting said element in a predeterminedarmed position in accordance with the latitude where the mine islaunched, and means carried by said arm for closing said firing circuitwhen the said element moves a predetermined distance in either directionfrom said armed position in response to a change in the magnetic field,said firing circuit including a timedelay device whereby said detonatoris not exploded until a predetermined time has elapsed after the closingof the firing circuit.

21. In a mine of the character disclosed adapted to be laid on the bedof a body of water adjacent the path of travel of a vessel, thecombination of an explosive charge, electro-responsive detonating meansadapted to explode said charge, a dip needle having a pivot bearing, a.shaft adapted to be horizontally disposed, means mounting said needle onsaid shaft for rotation therewith about an axis, a contact arm connectedto said needle and adapted to move in a plane upon rotation of saidneedle, a pair of contact elements disposed in said plane in the activepath of said first named contact and on opposite sides of said armrespectively, means for selectively biasin: said contact arm inaccordance with the strength and declination of the earths magneticfield where the mine is to be laid such that the contact thereon is in apredetermined position intermediate said pair of contact elements andnormally disengaged therefrom, and a firing circuit including a sourceof electrical power and operable upon engagement of said contact armwith either one of said contact elements to energize said detonatingmeans in response to the ma netic field of a vessel in the vicinity ofthe mine of sufiicient strength to change the setting of the dip needleto effect the engagement selectively of said contact arm and contactelements thereby to explode the mine.

References Cited in the tile of this patent UNITED STATES PATENTS953,191 Bergstrom Mar. 29, 1910 1,382,374 Maxim June 21, 1921 1,388,658Marshall Aug. 23, 1921

